Decorative sheet-like materials, such as wall coverings are well known in the art. Such sheet materials are generally formed of paper, plastic, metal foil, fabric material or some combination thereof having a pattern or design printed or embossed on the front surface, with the back surface being coated by the user with an adhesive, such as glue, cement, or the like (generally known as “wallpaper paste”) by which the wall covering may be bonded to a wall, ceiling or other target surface.
Other types of wall coverings include those having a plastic decorative surface and a backing of woven or non-woven fabric or paper. The back surface is adapted to be coated by the user with the adhesive set forth above in order to secure the wall covering to a surface. However, users dislike the inconvenience of mixing and applying the paste. Additionally, there are prepasted wall coverings available. However, these prepasted wall coverings need a water trough and this can be both time consuming and messy. Also, both the non-prepasted and prepasted wall coverings require the user to perform additional steps to apply the wall covering to the target surface. Generally, once these conventional wall coverings are applied to the target surface, only slight adjustments in their position upon the target surface may be made before the adhesive cures.
To eliminate the additional steps and mess of using “wallpaper paste”, wall coverings have attempted to use pressure sensitive adhesives. Pressure sensitive adhesives are known to provide immediate adhesion between two materials upon contact. Such adhesives rely on quick set-up reaction or rapid cure time for prompt adhesion. In the art of tapes, labels, wall coverings and other articles using pressure sensitive adhesives to adhere an adhesive coated surface to a target surface, there has been recognized the problem of premature adhesion or sticking to contact surfaces, such as a target surface. That is, before the adhesive coated surface can be properly positioned over a target surface, inadvertent contact of the adhesive with the target surface causes premature adhesion at one or more locations, thereby inhibiting proper positioning. For example, due to this premature sticking to the target surface, wall coverings are very difficult to apply to a wall and then reposition, as occurs when lining up the patterns of at least two wall covering sheets.
To reduce this premature adhesion to contact surfaces, pressure sensitive adhesive wall coverings have typically used adhesives with a low bond strength or tack to attach it to the target surface. However, this creates an additional problem in that the wall coverings lack sufficient tack to maintain attachment to the target surface for long periods of time. Because of this low tack, over a period of time the user experiences the wall covering peeling from the wall especially at the sheet margins.
However, pressure sensitive adhesives (“PSA”) with a higher bond strength or tack, i.e., aggressive or permanent pressure sensitive adhesives, generally have not been used to combat the problem of insufficient tack. This is due to the fact that these permanent PSA's are very tacky and tenacious and thus become very difficult to handle and use. For example, the wall covering will prematurely adhere to contact surfaces, such as the user's hands or the target surface. Once the adhesive has made premature contact with the surface, the user generally cannot remove the wall covering or even make slight adjustments in its position without destroying the wall covering or significantly reducing the bond strength. Therefore, most PSA wall coverings use low tack PSA's in an attempt to make the wall coverings easy to use. However, as mentioned above, even these low tack PSA's can cause the problem of premature adhesion to a contact surface. Although the user can generally separate the low bond strength wall covering from the contact surface without destroying the wall covering, it still frustrates the user and wastes the user's time.
Others have tried to solve the problem of premature adhesion to contact surfaces by applying a removable release paper to the adherent sheet material such as found for example in U.S. Pat. No. 5,487,929 issued to Rusincovitch, Jr. et al. on Jan. 30, 1996. However, this release paper adds additional costs to the sheet material and requires both the manufacturer and user to perform additional steps. Others have also tried to solve the specific problem of premature adhesion of a adherent, decorative sheet material by placing solid protrusions as spacers between the decorative sheet and the target surface such as also found in U.S. Pat. No. 5,487,929, issued Jan. 30, 1996, to Rusincovitch, Jr. et al. However, these protrusions are solid and thus require more material and do not completely collapse.
Still others have tried to solve the problem of premature adhesion of an adherent sheet material to contact surfaces by placing spacers to separate the pressure sensitive adhesive from the target surface, such as found, for example, in U.S. Pat. No. 4,376,440 to Whitehead et al., U.S. Pat. No. 5,141,790 to Calhoun et al., U.S. Pat. No. 4,959,265 to Wood et al., U.S. Pat. No. 5,344,693 to Sanders, U.S. Pat. No. 4,061,820 to Magid et al., and European Patent Application No. 0 623 332 A1 to Lauritzen. Generally, this art has focused on the use of stand-offs with pressure sensitive adhesives primarily in the area of sanitary napkins. However, different solutions are needed for flexible, adherent sheet materials having protrusions intended to be adhered to smooth or rigid surfaces. Commonly assigned, U.S. Pat. No. 5,662,758 issued to Hamiltion et al. on Sep. 2, 1997, and U.S. Pat. No. 5,871,607 issued to Hamilton et al. on Feb. 16, 1999, provide a thorough description of the art in adherent sheets protected from premature adhesion and are herein incorporated by reference.
Both of these commonly assigned patents involve adherent sheets which are protected from premature adhesion to a contact surface via hollow protrusions. However, generally, neither deal with wall coverings, labels or other adherent sheet materials having protrusions with either an additional substrate or a high bond strength.
It is well known in the art to bond a substrate to a flat film such as by laminating the two together using pressure and a laminating adhesive. However, if the film is formed with hollow protrusions then a problem exists in how to combine the substrate with the film that has hollow protrusions without crushing the film protrusions. Additionally, once the substrate is bonded to the film, an additional problem of air entrapment within the protrusions is created. For example, the substrate and potentially the laminating adhesive may now have created a gas barrier that prevents air from escaping from the protrusions when the protrusions are made to collapse. If the air does not escape from the protrusion, the protrusion may not fully collapse and thus prevent full adhesion of the sheet material to the target surface.
U.S. Pat. No. 5,906,883, issued May 25, 1999, to Blanc-Brude, discusses plurality of interconnected non-adherent elements made from a substrate. However, it is believed that this requires a difficult process to make.
Therefore, such adherent sheet materials leave room for improvement in ease of use and manufacture, cost, repositionability and bond strength.
Accordingly, it would be desirable to provide an improved multi-layered, adherent sheet material which is inexpensive to make, has means for protecting the adhesive from prematurely adhering to contact surfaces yet is efficient to store and ship.
It would also be desirable to provide such a material which is easily handled and manipulated by a user during the application process and is repositionable, yet forms an adequate bond with a variety of materials and surfaces to effectively adhere to the target surface.
It would also be desirable to provide a wall covering which is easily handled and manipulated by a user during the application process and is repositionable, yet forms an adequate bond against a variety of materials and surfaces to effectively adhere to the target surface.